Foam inhibited oil



' 2 Sheets-Sheet 1 INVENTORS Vic/0r M florsaf'f James a Clay/on B x U Arrorney v Filed July 14, 1942 V- N. BORSOFF El AL FOAM INHIBITED OIL \\&

Nov 18, 1947. I

E08 E21 5 -E2 Temperature Degrees Fahrenheit m m m w w m Patented Nov. 18, 1947 FOAM INHIBITED OIL Victor N. Borsoif and James 0. Clayton, Berkeley, Calif., assignors, by mesne assignments, to California Research Corporation, San Francisco, CaliL, a corporation of Delaware Application July 14, 1942, Serial No. 450,886

20 Claims.

, 1 W This invention relates to 011s. inhibited against the formation of a stable bubble. foam and to a method of inhibiting the foam formation tendency of oils.

On mixing oil with air, a certain amount of I base oils from which they are compounded. Thus petroleum lubricating oils compounded with metal naphthenates, higher metal alcoholates, higher metal alkyl phenates and metal salts of higher fatty acids foam more than the corresponding base oils. Many other additives cause more foam to be produced by oils to which they are added than is formed by the base oils.

Oil foaming, even with compounded oils which display the greatest tendency to foam, is not always troublesome. Under conditions of little or no agitation, for example, trouble due to foaming is encountered, if at all, only in very exceptional cases. On the other hand, certain drastic types of service, involving extremely violent intermixture of oil and air or combustion gases, may produce an objectionable amount of foam with many oils. Between the extremes, however, of service causing little foaming of any oil and service causing much foaming of many oils, there are types of service and certain oils which, when used in combination; cause considerable difiiculty. As stated, certain compounded oils exhibit a greater tendency to foam than the base oils, and

when these compounded oils are used in certain types of lubrication systems, involving greater agitation of the oil and greater intermixture with gases than the ordinary crankcase lubrication of automobiles, the greatest practical difficulty is encountered.

pacity; it pumps faster than required'to pump all of the available oil in the crankcase. It therefore pumps a great deal of air along with theoil, and this at a rapid rate, and the result is entrainment of air in the oil and the formation of foam. As a consequence, excessive foaming oocurs when oils such as the aforementioned compounded oils are used and oil is lost through the breather pipes, insumcient lubrication results because of the presence of air in the oil supplied to the motor, and other disadvantages result.

011 also forms a more persistent foam if itcontains water (as in solution) and is then heated and suddenly subjected to a very low pressure, as, for instance, in an airplane engine climbing from a low altitude to 40,000 feet at a high speed. In other instances, as in the lubrication of gears .with heavy oils, foaming difliculties may also be encountered.

It is an object achieved by the present invention to inhibit the foaming of oils.

It is a further object achieved by the present invention to inhibit the foaming of compounded mineral lubricating oils.

It is a still further and a particular.object achieved by the present invention to obviate the problem of excessive foaming of compounded mineral lubricating oils when used in types of lubrication service involving severe conditions of intermixture of oil and gases.

Other objects achieved by the invention will be apparent from the following description and from the claims.

We have discovered that foaming of oils can be inhibited by incorporating therein a small amount of a compound containing not less than about 15% by weight of oxygen and represented by the formula wherein A is an aromatic nucleus, X is an oxygen-containing substituent, R is a substituent selected from the group consisting of hydrogen, alkyl, aryl, aralkyl and cyclo-alkyl radicals, a is a whole number at least equal to l and b is zero or a whole number. The aromatic nucleus A may contain other substituents in addition to X and We have found that such oxygen-containing substituted aromatic compounds are effective in reducing foaming even when used in very small amounts, and that they are highly efi'ective in inhibiting the foaming of compounded lubricating oils when subjected to extreme agitation and intermixture with gases. They are, however, not limited in their efiectiveness to compounded oils but 'may be used to advantage wherever troublesome foaming of oils is encountered. Certain of Simple experiment will enable one to select the best inhibitor for the purpose at hand.

The class of inhibitors falling within the scope of the present invention will first be illustrated with reference to the component parts A, X and 3 (OR) and then with reference'to specific examples of such inhibitors.

The component A, which is an aromatic nu- 4 Still further examples of foam inhibitors are as follows:

, Carboxy acids Amylbenmlc acid cleus, may be, for example, the benzene nucleus Methoxyamylbenmc acid or a polycyclic aromatic nucleus such as the 5 Octylsalicylicacid y y p cac naphthalene nucleus, and the aromatic nucleus Esters may be substituted, in addition to the substitug e t y e te gt r wtg ylbe i z m ents X and OR, by any one or more of numerous g g ggggggg g; 33: 3? groups, such as alkyl, halogen, amino, nitro, etc. Butyl genzoate Methyl climate The component X, which must contain at least 10 gay gfiggg Egg} one oxygen atom, may be, for example, an hygrotpsl'lszllillc lgizge l zg gi-n igob m ll 58 C y -n 080 08 droxyl group, an ether group, any one of the octg'lsancglate Ethylwphemxybenmte groups COOR, RCOO, and -R C()OR, iii {mg}: Thyguglrybeigzoatet p-phfis honobtenzoate 6 y 111- y OXY 0112086 y D-Sll 0 Z088 Whereln R and R may be hydrocarbon or Substi' Octyl gallate Octyl2,3,4-trihydroxybenzoata tuted hydrocarbon residues; a ketone or an alde- Amylo-ac etylbciggoatem Mithylgiirylgte hyde group; a carbinol group, etc. W g g am ga The component OR may be lacking entirely Amyl-o-pyrocatechinate Daily ophltlhglate (b=zero) but preferably it is present (b=1 or Epggf E-tfittffiii 81%;? greater); that is, our foam inhibitors preferably Ethyl veratrate 131mm napllilthoillte contain a plurality of oxygen-containing sub- M fiirfi'lfitihm stituents attached to the aromatic nucleus A. Ethyl mesltylenato %t1l:y}hei;n1imellitate Typical examples of the component OR. are hy- Amylwthmybmmm Y droxyl, alkoxyl, aryloxyl, and cyclo-alkoxyl Phenols groups. Where R is a hydrocarbon radical it 61 5 3 g ggg gggggggg may contain substituent groups including oxy- Hydroqulnone Butylresorclnol gen-containing substituent groups such as hyggig g gg fig fgg g droxyl, aldehyde, ketone, carbinol and carboxy Methylpyrocatechol Ethylhydroquinone groups We? as estimat s? 11 1'0 one Specific examples typifying the class of inhibif h 'kesml gu mgi sm i ci l m 1'0 BXY y I'OXY Y OQU one tors which we have found to be effective are the 3 Dimethykesommd nmgdmxymphthalenes fOIIOWiIlgZ Dimethylhydroquinone Ant racenediol Per Cent Molec- Inhibitor Molecular Structure ular gn of Weight oxygen Benzaidehyde C 106 15.1

Saligenin OH 124 25.8

I CHQOH Methyl sallcylate OH 152 31. 6

COOCH:

Resorcinol monoacetate... OH 152 31. 6

Benzoyl acetone 162 i9. 8

C0.0H|.CQ.CH|

Amy] salioylate OH 208 23.1 A

Phenyl salieylate OH 214 22. 5

Naphthyl salicylate i OH 264 18.4

Ethers Methyl hen lather Pyroaitecholmonopro yl ether Guaiacof Besorcinolmonopropyfether Reccrcinolmonomethylether Hydroquinone monopropyl Hydroquinone inonomethyl other other Pyrocatechol monoamyl ether Resorclnol monoamyl ether Veratrol Resorcinol dimethyl ether Hydroquinone monoamyl ether Hydroquinone dimethyl ether ggrocatechol dibut lether Guaethol loroglucinoltriet ylether Resorcinol monoethyl ether 'Pyroga oi tributyl ether Dimethoxynaphthalene Hydroquinone monoethyl ether Aldehydes and ketones Amyl uinone l-hydroxy-2-naphthyl methyl Bali dehyde one Amy -p-hydroxyb'enzaldehyde Octylanthragallol Furyl phenyl ketone about 270. We also prefer to use as inhibitors.

those compounds which are soluble in mineral oilto the extent used. Less soluble inhibitors are more likely to be removed by filtration or to settle out on standing. However, oil solubility is not essential toeffectiveness in reducing foam and a solubility of the order of 0.001 per cent by weight based on the oil is adequate.

The inhibitors of our invention may be advantageously used in a wide variety of oils, including naphthenlc base, paraifln base and mixed base mineral oils, in synthetic oils, and in oils of viscosity ranging from 40 SSU or lower at 210 F. to 150 SSU or higher at 210 F.

Preferably the foam inhibitors of the present invention are used in the finished oil in an amount equal to about 0.001% to 1 per cent by weight based on the oil. If the oil is a compounded oil containing 0.1 to 5.0 per cent by weight of an additive which promotes foaming,

the foam inhibitor is preferably used in an amount equal to about 10 to 200'per cent by weight based on the additive.

Concentrated solutions of foam inhibitor in oil may be prepared. Such concentrates may also contain other compounding agents. By diluting the concentrate with more oil, a finished oil can be produced containing foam inhibitor, or foam inhibitor and other compounding agent or agents in the desired amount. Conveniently, concentrates containing from about 1.0 to per cent by weight of foam inhibitor based on the total concentrate are thus prepared, in cases where the foam inhibitor is sufliciently oil soluble.

The following specific examples will serve to illustrate the advantages and effectiveness of the inhibitors of the invention in reducing foam formation:

EXAMPLE I The foaming qualities of various oils were observed. The base stock was a solvent treated. paraffinic base oil having a viscosity of 120 SSU at 210 F.. and a viscosity index of 86. The first oil tested consisted of this base stock alone and the second oil consisted of the base stock compounded with 0.25 per cent by weight of a 2:1-

mixture of a calcium alkyl phenate and a calcium cetyl phosphate. The calcium alkyl phenate so used was the salt of an alkyl substituted phenol prepared by condensing butene polymers, having an average molecular weight of about 196, with phenol. The calcium cetyl phosphate so used was the salt prepared from a mixture of monocetyland dicetyl-phosphoric acids. The remaining oils each consisted of base stock. 0.25 per cent by weight of the same phenate-phosphate mixture, and 0.1 per cent by weight of a foam inhibitor. The test conditions were as follows:

500 cc. of the oil were placed in a cylindrical metal container 6 inches in diameter by 5 inches high and a "Mix-Master" stirrer of the type used in household kitchens was lowered into the oil. The oil was slowly heated by means of an electric hot plate and the amount of foam produced was measured at various temperatures up to 300 F. The speed of the stirrer was 1100 revolutions per minute. The test results at 275 F., under identical operating conditions except for variation of the oil composition, are set forth in Table I below: a

Table I Per cent increase in volume at 275 F. Uncompounded oil 11 Compounded oil 57 Compounded oil 0.1% benzaldehyde 29 Compounded 011 0.1% saligenln 17 Compounded oil 0.1% methyl salicylate 23 Compounded oil 0.1% resorcinol monoacetate 29 Compounded oil 0.1% benzoyl acetone 11 Compounded oil 0.1% amyl salicylate 47 Compounded oil 0.1% phenyl salicylate 29 Compounded oil 0.1% naphthyl salicylate 29 The, per cent increase in volume referred to in the above table, and again in Table II below, is arrived at by observin the increase in volume of the mixture of foam andoil over the original volume of oil, dividing the increase by the original volume ofoil, and multiplying by 100. It is, therefore, the volume of foam produced reckoned as per cent of the original volume of oil.

Exsmrra II 4 dropped from the reservoir through the drain to the sump at a rate controlled by the regulating valve. The pump in the return conduit was operated at a capacity three times the rate of flow of oil into the sump; therefore, both oil and air were pumped from the sump to the reservoir and foaming was caused in the reservoir. At the end of each 30 minutes of operation, the volume of foam and oil in the reservoir was observed. The amount of foam was calculated as the per cent increase in volume over the original volume of oil. Under identical operating conditions, various oils produced increases in volume as given in Table II below:

Table II Per cent increase in volume Uncompounded oil 30 Compounded oil 200+ Exmm III A 1939 Ford V-8, 85 horsepower engine was,

thus modified: The bottom of the crankcase was connected to a large glass container and the suction line of the oil pump was connected to the glass container. Oil dropping from the the moving parts drained from the crankcase through the pipe to the glass container and was pumped back to the engine from the glass container through the suction line. The air pressure in the crankcase was maintained at 1 inches of mercury. In this manner air became mixed with the oil draining from the crankcase and produced foam-in the glass container, where it could be observed.

Under identical operating conditions a compounded oil, and the same compounded oil plus 0.05 per cent of sallgenin, produced the following depths of foam in the glass container:

Depth of foam in inches Compounded oil 2.5 Compounded oil-+0.05% saligenin 0.5

above specific examples, amyl sallcylate is among the least effective of the inhibitors both in the open vessel-mechanical stirrer test (Example I) and in the sump test (Example 11) However, in both tests it efiects a substantial reduction in foaming. Benzoyl acetone is among the most effective foam inhibitors judged by either of these tests.

In addition to effectiveness in reducing foam formation, it is desirable that afoaminhibitorpossess certain other desirable properties. Among such additional properties are lackof objectionable odor, at least a slight solubility in lubricating oil, stability at high and at low temperatures, noncorrosiveness to bearings, such as alloy bearings, and good engine performance (that is, the inhibitor should not increase ring sticking, should not increase gum or resin formation on pistons or other hot parts of the engine, and should not increase wear). Also, it is desirable that the inhibitor be not subject to removal on filtering. The best inhibitor is, therefore, one which is highly effective in reducing foaming and which also possesses, in high degree, the desirable properties listed above. Saligenin, or ortho hydroxy benzyl alcohol, is,

from this standpoint, the best inhibitor. It is highly eifective in reducing foam, it lacks odor when present inmineral lubricating oil in small amount, it is sufliciently soluble in mineral lubricating oil, it is stable at low and at high temperatures, it is not removed by filtration of oil containing it, it is noncorrosive to alloy bearings, and it does not cause deterioration of engine performance.

We have observed that our inhibitors are more effective at elevated temperatures than at lower temperatures. At about the ordinary temperature, the reduction in foaming produced by the inhibitors of the invention is small, although substantial. At about 120 to150 F. the reduction of foaming begins to be large, and above about 150 F. the reduction in foaming is very large.

The effect of temperature upon foaming of un- 8 hibited and inhibited oils is shown by the accompanying drawings.

In Fig. 1,- abscissae represent temperature in degrees Fahrenheit and ordinates represent the volume of foam calculated as percentage on the original volume of oil. Curve A represents the uncompounded'oil of Example I, curve B represents the same oil compounded with 0.25 per cent 'by weight of a 2:1 mixture of calcium alkyl phenate and calcium cetyl phosphate (the same as used in Example I), and curve 0 represents the same compounded oil containing, in addition to the phenate and phosphate, 0.1 per cent of saligenin. The test conditions were they same as in Example I, except that observations were made at a number of different temperatures.

It will be noted that foaming was great in the case of all three oils at 80 F., though substantially less with oil A (uncompounded oil) and oil C (compounded oil containing saligenin) than with oil B (compounded 011 containing no saligenin). As the temperature increased, the foaming of all three oils decreased, but the foaming of oils A and C decreased more rapidly than that Fig. 1 of of oil B. At about 170 F., however, oil B began to foam more with increase in temperature whereas oils A and C continued to decrease in amount of foaming.

It will be noted that the inhibitor exerted great er effectiveness in reducing foam formation at higher temperatures than at lower temperatures.

From the standpoint of foam formation in internal combustion engines this is important. crankcase temperatures are generally above about 200 F., although the crankcases of some engines operate at temperatures as low as about 150 F. It is at temperatures above about 150 F.. especially above about 200 F., that excessive foaming is likely to occur. At these temperatures the inhibitors of our invention are highly effective in reducing foam formation.

The phenate-phosphate mixture referred to above is effective in inhibiting oxidation of lubrieating oils and in reducing ring sticking. It is given by way of example of the oil-soluble metal organic salts which are widely used in lubricating oils for such purposes. The tendency of such compounding agents to promote foaming detracts somewhat from their utility, and the obviation of this defect, by the use of our foam inhibitors. is one of the principal objects accomplished by the I invention.

It has been found that certain compounded oils which foam excessively also develop surfaces having the characteristics. of plastic solids; that is,

the surface is highly viscous, yields to and is deformed by a pressure in excess of a minimum y eld value, but does not flow freely like a liquid under the force of gravity. This fact has been brought to light through the use of the torsion pendulum. This apparatus and its use to determine surface plasticity and viscosity of aqueous solutions is described by R. E. Wilson and E. D. Ries in Surface films as plastic solids, Colloid Symposium Monograph, volume I, pages -173, published by the Department of Chemistry, University of Wisconsin 1923. The same apparatus and method were used to determine surface plasticity and viscosity of mineral oils.

Thus an SAE 30 blend of 70% Western acid treated naphthenic base oil and 30% Western parafinic base oil compounded with 6.25% by weight of a, 2:1 mixture of a calcium alkyi phenate and a calcium cetyl phosphate (the same as Example I) was investigated by means of the tor- 9 sion pendulum. The base oil is a non-foaming oil and the compounded oil exhibits a marked tendency to foam under the conditions of Example I. It was found that at room temperature the surface of the compounded oil, on ageing, became very viscous and similar to a plastic solid. However, when 0.1% of saligenin was dissolved in the compounded oil, a sharp initial rise in the viscosity of a freshly formed surface occurred and the surface became plastic. but after about 40 minutes the viscosity dropped off sharply and then more slowly. The surface became liquid again. The use of 0.2% of saligenin produced a similar result in less time.

A similar experiment at 200 F. revealed that the same compounded oil (lacking foam inhibitor) increased in surface viscosity during the first 2.5 minutes. remained constant for 1 minute and increased sharply between 3.5 and 4.0 minutes,

and that after 4 minutes the surface was a plastic solid. n dissolving 0.1% of saligenin in the cornpounded oil, the surface viscosity-time curve was found to be anomalous for the first 7 minutes, ex-

hibiting sharp drops and subsequent rises in viscosity. After about 9 minutes the surface began to set like a gel and become like a plastic solid, but a plastic solid having a very low yield point.

At both room temperature and200" F., therefore. a correlation was found between surface viscosity and foaming tendency; the excessively foaming 011 formed a surface, on ageing, similar to a plastic solid, but the foam inhibited oil formed a liquid surface on ageing at room temperature or a plastic solid surface of very low yield point onageing at 200 F.

Therefore, those oils whose surfaces on ageing (a matter of minutes) exhibit the properties of plastic solids with high yield points are excessively foaming oils, while oils whose surfaces on ageing remain liquid or exhibit the properties of plastic solids with very low yield points are not excessively foaming oils. The most probable explanation of these observed phenomena seems to be as follows: All oils, when agitated with air produce foam, which consists of small portions of air each surrounded by a film of oil: In many cases this foam is unstable, probably due to the instability of the film of oil. This film is so fluid that continued agitation and collisions of the foam bubbles with each other and the sides of the vessel and draining of the liquid from the film cause rupture of the film and destruction of the bubbles. In those cases, however, where the oil surface (hence the film of oil enclosing the air in the foam) is a plastic solid, the film is not as easily ruptured because the liquid cannot drain from the film due to capillary forces set up by the plastic solid surfaces, and the foam is stable. The plasticity and stability of the oil film clearly depend, in part at least, upon the nature and amount of solutes in the oil. Thus metal salts such as metal naphthenates, metal soaps of higher fatty acids, higher metalalkyl phenates, metal salts of phosphoric Our invention, however, is not limited in its application to those oils which, because of certain salt-like compounding agents, form viscous, plastic surfaces. Our invention is applicable broadly to the inhibition of oil foaming wherever it 00-. curs and comprises the addition of our foam inhlbiting agents to any oil which foams excessively.

For the purpose of clarity, the terms excessive foaming, excessively foaming, and, the like, as applied to oils herein and in the claims, refer to performance under the conditions of the following reproducible test, described with reference to Figs. 2 and 3 of the accompanying drawings. An oil which, when agitated under the conditions of this test at 275 F., increases in volume due to foaming by more than 20 per cent of its original volume, is an excessively foaming" oil, and oils which foam less than this amount are not excessively foaming oils.

I 500 cc. of oil are placed in a cylindrical fiat bottomed container 6" in diameter and 5 high (internal dimensions), the oil in the container is brought to and maintained at 275 F. by any suit-; able means such as a hot plate or a jacket, and the stirring elements of a Mix Master stirrer of the type used in household kitchens is lowered into the container. The Mix Master stirrer is the product of and obtainable from the Chicago acid partly esterified by long chain alcohols, and

in the film. or are themselves-adsorbed and coun-.

teract the adsorbed foam-producing salts.

Flexible Shaft Co., 1124 South Central Avenue, Chicago, Illinois. The stirring elements are similar in construction and action to the familiar household egg beater, consisting of two shafts oppositely rotated by a motor, and two elliptical loops attached to each shaft, one loop being at right angles to the other and the two loops having a common long axis. The dimensions and form of the vessel and stirring elements will be better understood, and can be duplicated by, reference to Figs. 2 and 3.

Fig, 2 shows, partly in cross section and partly in front elevation, the container and the stirring elements, while Fig. 3 shows in front elevation a detailed view of one-half of one loop of one stirring element.

Referring to Fig. 2, the apparatus comprises a cylindrical fiat bottomed container I and two stirring elements II constructed exactly alike. The internal dimensions of the container, as shown, are a diameter of 6" and a height of 5". The stirring elements consist each of an upper shaft A geared atthe top to a motor (not shown) and rigidly secured at the bottom to a lower shaft B and to'two elliptical loops C and D which are disposed at right angles to each other and have each the shaft B as their long axis and as a supporting member. Shaft B is rigidly secured to the tops and bottoms of loops C and D. In the preferred construction, as shown, shaft A is for example, a single shaft of'uniform diameter may take the place of'shafts A and B, passing,

through the tops of loops C and D and being secured thereto at the top and bottom of the loops. The stirring elements 11 areso placed in vessel I that shafts A are parallel and 1%" apart (center to center) and they are placed in vessel I so that a line drawn half way between and in the plane of the shafts colncideswith the axis ofvessel I, and the distance from the bottom of loops C to the bottom of vessel I is A. inch. The shafts A are so geared to the motor that they rotate at equal speeds in opposite directions.

Referring to Fig. 3, shafts A and B and one- 7 half of loop C are shown.- The other half of loop without altering substantially the results obtained.

In operation, the oil in container I is maintained at 275 F. and stirring elements A are rotated in opposite directions each at the rate of 1100 revolutions per minute. The volume increase due to foaming is determined by measuring the height of the oil before foam formation and after foam formation.

We claim:

1. A foam inhibited mineral 011, comprising a major quantity of an excessively foaming mineral oil of lubricating viscosity, and a minor quantity,

sumcient to inhibit foaming, of a compound whichcontains not less than about per cent by weight of oxygen, has a molecular weight not higher than about 270, and is,represented by the formula A(X) (0R)t wherein A is an aromatic nucleus, X is an oxygen-containing substituent, R is a member of the class consisting of hydrogen, alkyl, cycloalkyl, aryl and aralkyl radicals, and a and b' are integers.

2. A foam inhibited mineral oil, comprising a major quantity of an excessively foaming mineral oil of lubricating viscosity. and a minor quantity, suflicient to inhibit foaming, of a compound which contains not less than about 15 per cent by weight of oxygen, has a molecular weight not higher than about-270, and is represented by the formula .A(X)a(OR-)b where A is a benzene nusively, and under conditions of oil agitation and intermixture with gas which tend to cause excessive foaming, the method of inhibiting foaming of the lubricating oil, which comprises maintaining therein a small amount, suflicient to inhibit foaming, of a substituted aromatic compound containing not less than about 15 per cent by weight of oxygen, containing at least two oxygen atoms and having a molecular weight not higher than about 270.

6. A foam inhibited lubricating oil, comprising an excessively foaming hydrocarbon lubricating oil and a. small amount, sufllcient to inhibit foaming of the oil, of an aromatic compound of molecular weight not greater than about 270, containing at least two oxygen atoms and containing not less than about 15% by weight of oxygen.

7. A foam inhibited lubricating 011, comprising an excessively foaming hydrocarbon lubricating oil and a small amount, sufficient to inhibit foaming of the oil, of an aromatic compound of molecular weight not greater than about 2'70, containing at least two oxygen atoms, containing not less than about 15% by weight of oxygen and consisting of nonmetallic elements.

8. The oil of claim 7, wherein. said aromatic Y compound is present in the oil in the amount of cleus, X is a carbonand oxygen-containing substituent, R is a member of the class consisting of hydrogen, alkyl, cycloalkyl, aryl and aralkyl radicals, and a and b are integers.

3. A foam inhibited mineral oil, comprising a major quantity of an excessively foaming mineral oil of lubricating viscosity, and a minor quantity, suflloient to inhibit foaming, of a compound which contains not less than about 15 per cent by weight of oxygen, has a molecular weight not higher than about 2'70. and is represented by the formula ,A(X) norm wherein A is a benzene nucleus, X is a carboxy ester substituent, R is a member of the class consisting of hydrogen, alkyl, cycloalkyl, aryl, and aralkyl, and a and b are integers.

5. In thev lubrication of machinery at oil temperatures aboveabout 150 F. with compounded mineral oil lubricants which tend to foam excesabout 0.001 to 0.1 per cent by weight based on finished oil.

9. A foam inhibited lubricating oil, comprising an excessively foaming petroleum lubricating oil and a small amount, suflicient to inhibit foaming of the oil, of a compound, selected from the group consisting of derivatives of benzene and derivatives of natphthalene, said compound having a molecular weight not greater than about 270, containing at least two oxygen atoms, containing not less than about 15% by weight of oxygen and consisting of carbon, hydrogen and oxygen.

10. The oil of claim 9, wherein said compound is present in the oil in the amount of about 0.001 to 0.1 per cent by weight based on finished oil.

11. The oil of claim 9, wherein said compound is saligenin.

12. The oil of claim 9, wherein said compound is methyl salicylate.

13. The oilof claim 9, wherein said compound is benzoyl acetone.

14. A compounded lubricating oil comprising a hydrocarbon base oil, at least one salt selected from the group consisting of oil-soluble metal salts of organic acids and oil-soluble metal salts of organo-substituted inorganic acids, and a small amount, sufficient to inhibit foaming of the oil, of an aromatic compound of molecular weight not greater than about 270, containing at least two oxygen atoms and containing not less than about 15% by weight of oxygen.

15. A compounded lubricating oil comprising a. hydrocarbon base oil, at least one salt selected from the group consisting of oil-soluble metal salts of organic acids and oil-soluble metal salts of organo-substituted inorganic acids, and a small amount, suflicient to inhibit foaming of the oil, of an aromatic compound of molecular weight not greater than about 270, containing at least two oxygen atoms, containing not less than about 15% by weight of oxygen and consisting of nonmetallic elements.

16. A compounded lubricating oil comprising a petroleum lubricating oil, a foam-promoting amount of at least one salt selected from the group consisting of oil-soluble polyvalent metal salts of organic acids and oil-soluble polyvalent metal salts of organo-substituted inorganic acids,

18 said oil-soluble polyvalent metal salts being salts which promote foaming of the oil when the oil is subjected to violent intermixture with air, and a small amount, suflicient to inhibit foaming of the oil, of a compound selected from the group consisting of derivatives of benzene and derivatives of naphthalene, said compound having a molecular weight not greater than about 270, containing at least two oxygen atoms and consisting of carbon, hydrogen and oxygen.

1'1. A compounded lubricating oil comprising a petroleum lubricating oil, an oil-soluble polyvalent metal phenate and a small amount, sufllcient to inhibit foaming of the oil, of an aromatic compound having a molecularv weight not greater than about 270, containing at least two oxygen atoms, containing not less than about by weight of oxygen and consisting of nonmetallic elements.

- 18. A compounded lubricating oil comprising a petroleum lubricating oil, an oil-soluble polyvalent metal organo phosphate and a small amount, suflicient to inhibit foaming of the oil, of

an aromatic compound having a molecular weight not greater than about 270, containing at least two oxygen atoms, containing not less than about 15% by weight of oxygen and consisting of nonfor Signed and sealed numbered patent requiring correction as follows:

20. A compounded liquid lubricant comprising a major proportion of a petroleum lubricating oil containing an oil-soluble foam-promoting metal salt in an amount sufficient substantially to increase the tendency of the lubricating oil to foam excessively at temperatures above about 150 F. and under conditions of severe oil agitation and intermlxture with gas, and a minor amount, sufficient substantially to inhibit the said excessive foaming, of a compound which contains not less than about 15 per cent by weight of oxygen. has a molecular weight not higher than about 270, and is represented by the formula A(X) (OR)a wherein A is an aromatic nucleus, X is an oxygen-containing substituent, R is a member of the class consisting of hydrogen, alkyl, cycloalkyl, aryl and aralkylradicals, and a and b are integers.

VICTOR N. BORSOFF. JAMES O. CLAYTON.

' REFERENCES crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS metallic elements. Number Name Date 19. A compounded lubricating oil comprising 2,261,047 Anefl Oct. 28, 1941 a petroleum lubricating oil, a small amount each, 2,031,986 Stratford Feb. 25, 1936 suflicient to stabilize the oil and to inhibit piston Re. 22,189 Prutton Sept. 29, 1942 discoloration and piston ringstickingin an internal 2,298,465 Clapsadle Oct. 13, 1942 combustion engine, of an oil-soluble polyvalent 1,826,897 'Rice Oct. 13, 1931 metal phenate and an oil-soluble polyvalent 1,981,506 Hansen Nov. 20, 1934 metal organo phosphate, and a small amount, 2,045,551 Iddings June 23, 1936 suflicient to inhibit foaming of the oil, cf'an aro- 2,134,554 Grobel Oct. 25, 1938 matic compound having a molecular weight not 2,215,590 Maverick Sept. 24, 1940 greater than about 270,, containing at least two 2,320,263 Carlson May 25, 1943 oxygen atoms, containing not less than about 2,134,736 Renter Nov. 1, 1938 1 y weight of oxygen and consisting of non- 40 2,145,971 Cantrell Feb. 7, 1939 metallic elements. 2,216,711 Musher Oct. 1, 1940 Certificate of Correction Patent N 0. 2,430,857. 1 November 18, 1947.

VICTOR N. BORSOFF ET AL. It is hereby certified that error appears in the grinted specification of the above olumn 3, in the fourth formula,

Record no! museum 01! with this correction therein that the the Patent Oflice.

this 27th day of January, A. D. 1948.

Mm 0mm of PM. 

